IVF treatment involves several rounds of injectable medications given at different stages, each with a specific job. Most people go through three to four phases of injections over roughly four to six weeks: ovarian stimulation shots to grow multiple eggs, a suppression medication to prevent early ovulation, a precisely timed trigger shot to mature the eggs before retrieval, and progesterone support afterward to prepare the uterus for an embryo. Here’s what each phase involves and what it feels like.
Ovarian Stimulation Injections
The largest block of injections in an IVF cycle are the stimulation medications, often called gonadotropins. These are synthetic versions of the hormones your pituitary gland naturally produces to grow egg-containing follicles in the ovaries. In a normal menstrual cycle, your body matures just one egg. The goal of stimulation is to push multiple follicles to develop at once so your doctor can retrieve several eggs at one time.
The active hormones in these shots are FSH (follicle-stimulating hormone) and sometimes LH (luteinizing hormone). Common brand names include Gonal-F, Follistim, and Menopur, which contains both FSH and LH. The typical starting dose is around 150 international units per day for an average responder, though your clinic may prescribe anywhere from 100 to 450 units depending on your age, hormone levels, and how your ovaries respond. Stimulation injections are given once or twice daily for about 8 to 14 days.
These are subcutaneous injections, meaning a short, thin needle goes just under the skin. Most people inject into the lower belly, a couple of inches from the navel, or the front of the thigh. Some brands come in pre-filled pen devices similar to insulin pens, which makes self-injection more straightforward. During this phase, you’ll have frequent ultrasounds and blood draws so your clinic can track follicle growth and adjust your dose.
Suppression Medications to Prevent Early Ovulation
Once your follicles start growing, your body may try to ovulate on its own before retrieval. To prevent that, you’ll add a second injection called a GnRH antagonist. The two common brands are Cetrotide and Ganirelix. These block the hormonal signal that would trigger premature ovulation, keeping your eggs safely in the follicles until retrieval day.
Antagonist injections typically start around day five or six of stimulation and continue daily until the trigger shot. They’re also subcutaneous and usually given in the belly. Some protocols use a different approach, starting a GnRH agonist (like Lupron) earlier in the cycle to suppress ovulation. Your clinic chooses the protocol based on your medical profile, but the antagonist protocol is the most widely used today.
The Trigger Shot
The trigger shot is a single, precisely timed injection that tells your eggs to complete their final stage of maturation. Without it, the eggs inside your follicles wouldn’t be mature enough to fertilize. It also sets the retrieval clock: egg retrieval is scheduled exactly 34 to 36 hours after the trigger, so timing matters down to the hour.
There are two main types. The traditional trigger is hCG (human chorionic gonadotropin), sold under brand names like Pregnyl, Novarel, and Ovidrel. hCG acts directly on the ovaries to prompt egg maturation, mimicking the natural LH surge that causes ovulation. The alternative is a Lupron trigger, which works differently. Instead of acting on the ovaries directly, it signals your pituitary gland to release a burst of your own LH and FSH, producing a more natural ovulatory response.
Your doctor may choose a Lupron trigger if you’re at higher risk for ovarian hyperstimulation syndrome, since it causes a shorter, milder hormonal surge. Some protocols use both a Lupron trigger and a low dose of hCG together. The hCG trigger can be either subcutaneous or intramuscular depending on the brand. Ovidrel is a prefilled subcutaneous syringe, while Pregnyl is typically mixed from a powder and injected intramuscularly in the upper buttock area.
Progesterone Support After Retrieval
After egg retrieval, your body needs progesterone to thicken the uterine lining and support an embryo if it implants. In a natural cycle, the follicle that released the egg produces progesterone on its own. But because IVF disrupts that process, supplemental progesterone is standard.
The injectable form is progesterone in oil, given as an intramuscular shot in the upper buttock. These use a longer needle than the stimulation shots and are the injection most people find uncomfortable. The oil is thick, and the injection site can become sore, especially after weeks of daily shots. Progesterone support typically starts the day after retrieval and continues through the first 8 to 12 weeks of pregnancy if the transfer is successful.
The good news: vaginal progesterone (suppositories, inserts, or gel) is a well-established alternative. A study of 745 patients comparing vaginal progesterone to progesterone-in-oil injections found no difference in pregnancy rates (51% vs. 53%), miscarriage rates, or live birth rates. Many clinics now offer vaginal progesterone as a first-line option, which eliminates the intramuscular shots entirely.
What the Injections Feel Like
Most IVF injections are subcutaneous, and the needles are small. People often describe the sensation as a brief pinch or sting. Some women experience local skin irritation, small bruises, or redness at the injection site. The hormones themselves can cause breast tenderness, headaches, bloating, and mood swings. True allergic reactions to the medications are extremely rare.
The intramuscular shots, particularly progesterone in oil, are the ones most often described as painful. Warming the oil between your hands, icing the area beforehand, and having a partner help with the injection can make a noticeable difference. Some people develop small lumps at the injection site over time, which gentle massage and a heating pad can help resolve.
Ovarian Hyperstimulation Syndrome
The most significant risk from IVF injections is ovarian hyperstimulation syndrome, or OHSS, where the ovaries overreact to stimulation hormones and swell significantly. Moderate to severe OHSS occurs in roughly 1% to 5% of IVF cycles. Symptoms include abdominal bloating and pain, nausea, rapid weight gain from fluid retention, and in severe cases, difficulty breathing. Mild bloating during stimulation is common and expected, but sharp pain, vomiting, or sudden weight gain of more than two pounds per day warrants a call to your clinic. Modern protocols, including the use of Lupron triggers and lower medication doses, have made severe cases much less common than they once were.
Storing Your Medications
IVF medications arrive in a surprisingly large box, and storage requirements vary by drug. Unmixed powder vials of FSH medications like Follistim and Gonal-F can stay at room temperature, but the pre-filled pen cartridges (Follistim AQ, Gonal-F AQ) need refrigeration at all times. Once you mix any multi-dose vial with its diluent, it goes in the fridge. Lupron must be refrigerated. Progesterone suppositories are waxy and will melt if left out, so they belong in the refrigerator too. Progesterone in oil, by contrast, stays at room temperature. Your pharmacy will typically include storage instructions with each medication, and your nurse coordinator will walk you through the specifics during your injection teaching appointment.
A Typical Injection Timeline
Putting it all together, here’s what a standard antagonist protocol looks like week by week:
- Weeks 1 to 2: Birth control pills to synchronize your cycle and quiet the ovaries before stimulation begins.
- Weeks 3 to 4 (stimulation days 1 through 10 or so): Daily subcutaneous injections of FSH, sometimes with LH. Around day 5 or 6, the antagonist injection is added. You’re now doing two to three shots per day.
- Trigger night: A single injection timed for exactly 36 hours before your retrieval appointment.
- Day after retrieval onward: Daily progesterone, either as an intramuscular injection or vaginal insert, continuing for weeks if pregnancy occurs.
The total number of injections varies, but most people give themselves somewhere between 30 and 90 shots over the course of a full cycle. That range depends on how many days of stimulation you need, which progesterone method you use, and whether your protocol includes additional medications. It sounds like a lot, and it is, but most people find that the anxiety about injections is worse than the injections themselves, especially after the first few days become routine.